Why does my BB show the wrong senders name in emails?

in Outlook some users are getting an Mail from one Service account (Service.xy@office.de) with the right Sender address. The same mail at their BB are having an different Sender address from different users of our active Directory. For Example Johne.Doe@office.de. But if they are replying on this message the right address is shown (Service.xy@office.de).
In BB is there an Cache or an temporary addressbook which has saved the wrong name to the right address? It Looks like an wrong Name Resolution.
Does someone know the Problem?